| Message ID | 20250409-efidrm-avoid-uninit-screen_info-warning-v1-1-67babb19d831@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/sysfb: efidrm: Avoid clang -Wsometimes-uninitialized in efidrm_device_create() | expand |
Hi thanks for the fix. Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> with a remark below. Am 09.04.25 um 21:03 schrieb Nathan Chancellor: > Clang warns (or errors with CONFIG_WERROR=y): > > drivers/gpu/drm/sysfb/efidrm.c:353:11: error: variable 'screen_base' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized] > 353 | else if (mem_flags & EFI_MEMORY_WB) > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > drivers/gpu/drm/sysfb/efidrm.c:356:7: note: uninitialized use occurs here > 356 | if (!screen_base) > | ^~~~~~~~~~~ > drivers/gpu/drm/sysfb/efidrm.c:353:7: note: remove the 'if' if its condition is always true > 353 | else if (mem_flags & EFI_MEMORY_WB) > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > 354 | screen_base = devm_memremap(&pdev->dev, mem->start, resource_size(mem), > drivers/gpu/drm/sysfb/efidrm.c:261:27: note: initialize the variable 'screen_base' to silence this warning > 261 | void __iomem *screen_base; > | ^ > | = NULL > > efidrm_get_mem_flags() can only return a mask that has at least one of > the tested values set so the else case is impossible but clang's static > analysis runs before inlining so it cannot know that. Right, the variable mem_flags should always be set and thus screen_info should be mapped. I never got this error with gcc. > > Initialize screen_base to NULL and add a defensive print in case > mem_flags were ever returned without one of the four valid values. > > Fixes: 32ae90c66fb6 ("drm/sysfb: Add efidrm for EFI displays") > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- > drivers/gpu/drm/sysfb/efidrm.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/sysfb/efidrm.c b/drivers/gpu/drm/sysfb/efidrm.c > index af90064a4c04..7d820f42956b 100644 > --- a/drivers/gpu/drm/sysfb/efidrm.c > +++ b/drivers/gpu/drm/sysfb/efidrm.c > @@ -258,7 +258,7 @@ static struct efidrm_device *efidrm_device_create(struct drm_driver *drv, > struct drm_sysfb_device *sysfb; > struct drm_device *dev; > struct resource *mem = NULL; > - void __iomem *screen_base; > + void __iomem *screen_base = NULL; > struct drm_plane *primary_plane; > struct drm_crtc *crtc; > struct drm_encoder *encoder; > @@ -353,6 +353,8 @@ static struct efidrm_device *efidrm_device_create(struct drm_driver *drv, > else if (mem_flags & EFI_MEMORY_WB) > screen_base = devm_memremap(&pdev->dev, mem->start, resource_size(mem), > MEMREMAP_WB); > + else > + drm_warn(dev, "unhandled mem_flags: 0x%llx\n", mem_flags); This message should be something like drm_err("invalid mem_flags ..."). It's really a driver bug. Would you send an update? Best regards Thomas > if (!screen_base) > return ERR_PTR(-ENOMEM); > iosys_map_set_vaddr_iomem(&sysfb->fb_addr, screen_base); > > --- > base-commit: e8bf4a1bdaeadb28d13b9a2bcfd5910fda06eede > change-id: 20250409-efidrm-avoid-uninit-screen_info-warning-d62ef67ce3c5 > > Best regards,
diff --git a/drivers/gpu/drm/sysfb/efidrm.c b/drivers/gpu/drm/sysfb/efidrm.c index af90064a4c04..7d820f42956b 100644 --- a/drivers/gpu/drm/sysfb/efidrm.c +++ b/drivers/gpu/drm/sysfb/efidrm.c @@ -258,7 +258,7 @@ static struct efidrm_device *efidrm_device_create(struct drm_driver *drv, struct drm_sysfb_device *sysfb; struct drm_device *dev; struct resource *mem = NULL; - void __iomem *screen_base; + void __iomem *screen_base = NULL; struct drm_plane *primary_plane; struct drm_crtc *crtc; struct drm_encoder *encoder; @@ -353,6 +353,8 @@ static struct efidrm_device *efidrm_device_create(struct drm_driver *drv, else if (mem_flags & EFI_MEMORY_WB) screen_base = devm_memremap(&pdev->dev, mem->start, resource_size(mem), MEMREMAP_WB); + else + drm_warn(dev, "unhandled mem_flags: 0x%llx\n", mem_flags); if (!screen_base) return ERR_PTR(-ENOMEM); iosys_map_set_vaddr_iomem(&sysfb->fb_addr, screen_base);
Clang warns (or errors with CONFIG_WERROR=y): drivers/gpu/drm/sysfb/efidrm.c:353:11: error: variable 'screen_base' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized] 353 | else if (mem_flags & EFI_MEMORY_WB) | ^~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/sysfb/efidrm.c:356:7: note: uninitialized use occurs here 356 | if (!screen_base) | ^~~~~~~~~~~ drivers/gpu/drm/sysfb/efidrm.c:353:7: note: remove the 'if' if its condition is always true 353 | else if (mem_flags & EFI_MEMORY_WB) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 354 | screen_base = devm_memremap(&pdev->dev, mem->start, resource_size(mem), drivers/gpu/drm/sysfb/efidrm.c:261:27: note: initialize the variable 'screen_base' to silence this warning 261 | void __iomem *screen_base; | ^ | = NULL efidrm_get_mem_flags() can only return a mask that has at least one of the tested values set so the else case is impossible but clang's static analysis runs before inlining so it cannot know that. Initialize screen_base to NULL and add a defensive print in case mem_flags were ever returned without one of the four valid values. Fixes: 32ae90c66fb6 ("drm/sysfb: Add efidrm for EFI displays") Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- drivers/gpu/drm/sysfb/efidrm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- base-commit: e8bf4a1bdaeadb28d13b9a2bcfd5910fda06eede change-id: 20250409-efidrm-avoid-uninit-screen_info-warning-d62ef67ce3c5 Best regards,